import java.util.Scanner;

public class XiaoMingBuysComputer {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int computerPrice = scanner.nextInt();
        
        // 验证输入的价格是否符合要求
        if (computerPrice <= 0 || computerPrice > 100000) {
            System.out.println("输入的价格不正确，请输入1到100000之间的数字。");
            return;
        }
        
        int day = 0;
        int totalMoney = 0;
        
        // 逐天计算累积金额，直到达到或超过电脑的价格
        while (totalMoney < computerPrice) {
            day++;
            totalMoney += day;
        }
        
        System.out.println(day);
        scanner.close();
    }
}